1. Field of Invention
The present invention relates to a fuse circuit. More particularly, the present invention relates to a fuse circuit having a multi-state resistance value.
2. Description of Related Art
In recent years, the fuse circuit has been widely used in memory devices to serve as a one time programming (OTP) memory unit. When the current flowing through the fuse has a current value greater than the critical value, the fuse blows and the resistance value of the fuse is increased. Therefore, the original resistance value of the fuse and the increased resistance value of the fuse respectively represent two logic states, for example, the low resistance state and the high resistance state respectively represent a logic 0 state and a logic 1 state.
However, when the traditional fuse circuit is programmed, the fuse cannot be re-written once it is written (is blown out). Hence, multiple time programming cannot be performed and a multi-state resistance value is not obtained.